The present invention is directed to a cellular backup for conventional security alarm systems which utilize a digital communicator or telephone tape dialer to call a central alarm station when an alarm condition is present in a home, office or the like. The digital communicator or telephone tape dialer will, upon receipt of an alarm signal, automatically dial the central alarm station which, in turn, will dispatch security personnel to the site and/or notify the local police department. The digital communicator or telephone tape dialer is coupled to an 8-lead line called a DB-8 cord, which, in turn, is coupled to an RJ-31X jack required by the telephone company for use with alarm systems. The digital communicator is, in the conventional system, interposed between the DB-8 cord and the land-based phone or phones on the site to be protected by the alarm system so that under normal, non-alarm conditions, the phones at the site may be used in their normal manner. Upon the detection of an alarm signal at any one of the plurality of zones monitored by the alarm control system, which signal is inputted to the appropriate inputs of the digital communicator or telephone tape dialer, the digital communicator or telephone tape dialer will automatically switch over and take control of the telephone system, and will send out a call over the land-based telephone line to the central alarm station, indicating the presence of an alarm signal, as well an any appropriate information such as the zone effected, and the link.
Conventional, prior art alarm systems incorporating a digital communicator or telephone tape dialer, however, suffer from the disadvantage that, if the land line were to be cut or become inoperative for whatever reason, the digital communicator or telephone tape dialer would not be able to send out the alarm call. Thus, absence of the land line would effectively render the site unprotected, since no outgoing call could be made, by which the digital communicator or telephone tape dialer effects its operation. Therefore, if the land line were inoperative the digital communicator or telephone tape dialer would be useless.
The present invention is directed to a backup system which automatically takes control upon the inoperativeness of the land line connected to the convention telephone system, so that the digital communicator or telephone tape dialer may, alternatively, transmit its message over the cellular network, independent of the land-based telephone line system, and thereby prevent any prolonged lapse of time that the site is left unprotected by the alarm system using land-based lines alone.